Mark Zenier wrote in message
...
In article , N_Cook wrote:
Like breaking a combination lock you need a "tell " to work on.
Assuming a piece of kit, impossible to get a remote control for and
"universal " remotes do not register any change to the otherwise dead
kit.
If you broke into a ground or supply line to the microcontroller and
monitored the supply current , would there be staged changes of current
when
exercised by various , but vast majority wrong, IR signals?
ie simple swept 30 to 50 KHz oscillator source would you pick up on say
38KHz as the basic required "carrier" frequency ?
Varying mark/space of gated pulses at that "carrier" f, would you pick up
on
the correct mark/space
?

On the receiver side, the IR detector module (or optical IC) contains the
AM tuned receiver and outputs the demodulated baseband digital signal.
All the microcontroller will see is the coding, not the carrier.
With about a 1 kHz bandwidth. It's ttl or open collector digital output.

The modules come fixed tuned for a large number of frequencies, from about
20 kHz to 100 kHz. Sharp made a lot of the modules. I think Infineon
made the IC versions. You could point a modulated LED at the reciever
module and find the carrier frequency by sweeping the LED drive frequency
and looking at the module output.

Then would there be a recognisable respone to various random "nibbles"
that
are parts of the required coding ?

Each message usually has all sorts of error detecting or correcting bits.
Often in the form of repeating the data, inverted. Or checksums or
crcs, stuff designed to prevent false operations. With about 10 to 30
bits per message, finding it by random would be too much to hope for.
In the old days with dedicated chipsets, you could read the datasheet,
but now the transmitter could be a cheap micro.

Different manufacturers had standard multifunction message protocols.
Elektor published a number of the different message formats, (Philips
and Sony, I think). But for odd gear, only the software guys who wrote
the firmware would know.

Back in the first few issues, back in the late 1980's, Circuit Cellar
Ink magazine had a project for a universal recording remote control.
But you would need a working remote for that.

Mark Zenier
Googleproofaddress(account:mzenier provider:eskimo domain:com)



Hopefully I can get back to this hobby on Sunday , target kit I
serendipituosly had one function triggered by these codes
11222322412313211
then
11521322X6112615
or also
11521322X6165
all for various apparatus in search mode of a "universal"
presumably the second trigger is 11521322X61
where X is 1010 ..... ten times, 3 is 101010 etc
if I had gone through the search sequence the other way then there would
have been no response.
I have yet to optimise the model code and then open out for the function
codes before sending to a learner. Optimised as only a small section of
those paired codes is probably active and the tops or tails or both are
ignored

Another thing to explore is a basic satellite R/C here, which is hopeless as
half of all remotes affect a channel change on it and the reverse , its r/c
makes some sort of change on all sorts of equipment. So will have to explore
the coding on that to see why it has a semi master key function.